Washington (CNN) -- The rape of a child may be linked to a gap in a program intended to remove criminal aliens from the country.

Under the federal Secure Communities program, law enforcement agencies run the fingerprints of people they arrest against immigration databases, aiming to find illegal immigrants. The most dangerous are then removed from the country by Immigration and Customs Enforcement.

Law enforcement personnel working on the rape of an 8-year-old girl say a person arrested Sunday evening in Houston is an illegal immigrant who slipped through the system.

The suspect, Salvador Portillo-Saravia, has been charged with one count of rape and one count of sodomy, according to Don Gotthardt, spokesman for the Fairfax County, Virginia, Police Department. He could be extradited back to Virginia later this week.

If the system had worked the way it was supposed to, Portillo-Saravia might have been held in custody for the federal immigration agency, and possibly deported, after an arrest for drunkenness. Instead, he was released.

The rape took place the day after Christmas in Centreville, Virginia.

Portillo-Saravia's arrest for public drunkenness was in November in neighboring Loudoun County, Virginia.

When he was taken to the Loudoun County jail, his electronic fingerprints were run against federal immigration databases under the Secure Communities program. Since the program was put in effect in 2008, 81,000 illegal immigrants have been removed from the country, federal officials say.

Portillo-Saravia's prints did not get a hit.

"Everything came back negative, so by law, obviously, when the alcohol wears off, he is released," said Sheriff Stephen Simpson.

But there should have been a hit. Portillo-Saravia had been deported from the United States in 2003.

Why didn't the fingerprints taken from him at that time show up in the system?

A senior Immigration and Customs Enforcement official says technology is the issue. In 2003, Portillo-Saravia's fingerprints were taken the old-fashioned way, with ink. They were never digitized and put in the agency's electronic database.

If Loudon County had had special concerns about Portillo-Saravia, it had another tool.

The senior immigration official says that in more than 300 other cases, the Loudoun County Sheriff's Office asked the agency to do additional, manual checks of immigration records.

But the sheriff said nothing about Portillo-Saravia raised any red flags.

He also said he didn't know about the need to check anything beyond the electronic database.

"The process we followed is the process we are supposed to follow. We assumed that 'all prints' meant all prints. We didn't know that there were other prints in the system that needed to be checked manually," Simpson said.

Immigration and Customs Enforcement's online materials about Secure Communities -- a program whose effectiveness has been lauded by officials in both the Bush and Obama administrations -- don't mention the need to check older prints manually. In fact, the agency said Secure Communities will eliminate the need for "time-consuming manual inquiries."

The agency now said it will enhance its "communication, training and outreach" to clarify the need to check nondigitized records.

Immigration and Customs Enforcement does not have a timeline to move its thousands upon thousands of ink fingerprints to its electronic database, a lengthy process.